1. Field of the Invention
The present invention relates to a backlight assembly and a liquid crystal display (LCD) apparatus having the backlight assembly. More particularly, the present invention relates to a backlight assembly that is capable of reducing the leakage current of a lamp, and an LCD apparatus having the backlight assembly.
2. Description of the Related Art
Recently, there has been much technical progress made with information-processing devices. As a part of this progress, much progress has also been made to display apparatuses that interface the data that is processed by the information-processing devices to convert the data to a user-recognized format.
An LCD apparatus, which is known for advantages such as light weight, small size, full-color, high resolution, etc., has been widely used in display apparatuses. The LCD apparatus converts variations of optical characteristics of a liquid crystal (LC) cell into visual variations. Since the LCD apparatus does not generate light on its own, a backlight assembly is employed in the LCD apparatus to act as the light source. The LCD apparatus displays an image by using the light from the backlight assembly.
The backlight assembly is classified as either a direct illumination type or an edge illumination type in accordance with positions of the light source. The direct illumination type backlight assembly includes a light source positioned under an LCD panel. Light emitted from the light source is directly irradiated onto an entire surface of the LCD panel. Since the direct illumination type backlight assembly utilizes more light sources than those of the edge illumination type backlight assembly, the direct illumination type backlight assembly generally has a higher luminance than the edge illumination type backlight assembly.
The direct illumination type LCD apparatus includes an LCD panel displaying an image and a backlight assembly providing the LCD panel with light.
FIG. 1 is a partial cross sectional view illustrating a conventional backlight assembly.
Referring to FIG. 1, a conventional backlight assembly includes a lamp 10, a light-diffusing member 30 placed over the lamp 10, a bottom chassis 50 located under the lamp 10, and a reflection plate 20 on the bottom chassis 50. Electrons move in the lamp 10 so that a current flows in the lamp 10. Meanwhile, since the bottom chassis 50 includes a conductive material, the lamp 10 and the bottom chassis 50 form a capacitor so that a leakage current is generated from the lamp 10. In general, the capacitance of the capacitor is inversely proportional to the distance between electrodes.
FIG. 15 is a graph illustrating luminance variations with respect to a length of the lamp from a first end to which a high voltage is applied to a second end to which a low voltage is applied. In FIG. 15, line I represents the luminance of the lamp 10 when a distance between the lamp 10 and the bottom chassis 50 is about one millimeter. Line II indicates the luminance of the lamp 10 when a distance between the lamp 10 and the bottom chassis 50 is about three millimeters. Line III represents the luminance of the lamp 10 when a distance between the lamp 10 and the bottom chassis 50 is about five millimeters. Line IV indicates the luminance of a separate lamp that is not assembled with a bottom chassis. As shown, the first ends of each of the lamps 10 have luminance levels higher than the first end of the separate lamp (IV). This is caused by increasing a current that is applied to the first ends of the lamps 10 to obtain a tubular current of about six milliamperes at the second ends of the lamps.
As shown in FIG. 15, the leakage current, which is indicated by the luminance drop with the length of the lamp, is reduced proportionally to an increase in the distance L1 between the lamp 10 and the bottom chassis 50. Thus, to obtain substantially the same tubular current at the second end of the lamp 10 as at the first end of the lamp 10, the initially applied high voltage is proportionally increased, as is the distance L1 between the lamp 10 and the bottom chassis 50. Thus, the distance L1 between the lamp 10 and the bottom chassis 50 is an important parameter for controlling the leakage current.
To prevent or reduce the leakage current of the lamp 10, the distance L1 between the lamp 10 and the bottom chassis 50 is increased. However, the lengthening of the distance L1 causes an increase of a thickness of the LCD apparatus. Thus, a method that allows a reduction in the lamp current leakage without undesirably increasing the thickness of the LCD apparatus is desired.